Method of manufacturing encapsulated components



April 4, 1967 W. M. ROBINSON METHOD-OF MANUFACTURING ENCAPSULATEDCOMPONENTS Original Filed July 50, 1962 FIG. 4

BY g4! ATTORNEY United States Patent 3,311,967 METHOD OF MANUFACTURINGEN CAPSU- LATED COMPONENTS William M. Robinson, Fairhaven, Mass.,assignor to Corneil-Duhilier Electric Corporation, a corporation ofDelaware Original application July 30, 1962, Ser. No. 213,305, nowPatent No. 3,236,936, dated Feb. 22, 1966. Divided and this applicationAug. 23, 1965, Ser. No. 493,953 2 Claims. (Cl. 29155.5)

This application is a division of my application Ser. No. 213,305, filedJuly 30, 1962, now US Patent No. 3,236,936, entitled, MiniatureElectrical Component With Protected Terminal-Wire Connections.

The present application relates to electrical components andparticularly to capacitors.

The following discussion is addressed particularly to encapsulatedcapacitors inasmuch as the invention has special application tocapacitors. However, except where the context may so require, theillustrative disclosure is not to be construed as limiting.

In the manufacture of capacitors, among the various critical problemsare the provision of a connection between a terminal wire and a film orfoil electrode of the capacitor section. Another problem involves theprovision of an insulating case for the capacitor that will excludedeleterious moisture. An object of the present invention resides in theprovision of a novel encapsulated component affording vastly improvedresistance to mechanical damage, to the moisture-proof characteristic ofthe encapsulation, and to the terminal connections, where mechanicalstresses may be imposed on the leads or terminal Wires that extendexternal of the encapsulated unit.

The illustrative embodiment of the invention includes a wound capacitorunit of the so-called extended-foil type. Lead wires are joined to thewound section and extend away from the section parallel to each other. Awafer of a tough material such as nylon is disposed adjacent thecapacitor section and has holes through which the wires extend. Thecapacitor section, the wafer and portions of the lead wires that extendthrough the wafer to the capacitor section are encapsulated within ahard moistureexcluding insulation that is applied as a coating.

The wafer is extremely tough and, before it is encapsulated, it mayreadily be twisted and flexed. The encapsulating coating is also quitebrittle, separately. However, where the insulating wafer is containedand encapsulated in the same coating that encapsulates the capacitorsection, the wafer and the insulating coating are each effective tomodify the characteristics of the other. As a result, mechanicalstresses imposed on the leads have no tendency to twist or bend thewafer that is separately susceptible to bending and twisting, and theleads have no tendency to crack the encapsulation formed about thecapacitor section when the leads are constrained by the encapsulatedwafer. Further, the encapsulated wafer adjacent the capacitor sectionprevents stresses imposed on the external portions of the wire frombeing applied to the joints between each wire and the foil of thecapacitor section. This latter consideration is of special concern where(as in the illustrative embodiment below) very small components areinvolved, and where the joint between the wire and the section terminalis of a character that is inherently weak mechanically.

In the manufacture of a capacitor of the foregoing construction, as willbe seen in the illustrative disclosure which follows, the capacitorsection is interposed between the ends of the lead wires while thosewires extend through spaced-apart holes in the insulating wafer, thewires being thereby accurately spaced. While being thus held, joints aremade between the ends of the wires and the terminals of the capacitorsection. In one form, the joint may be made by electrically welding thewires to the extended foils of the capacitor section, or a solderingoperation might he used. However, the connection is made, with spacialadvantage, by means of a conductive thermalsetting resin such asconductive epoxy paste. It is clear, accordingly, that the insulatingwafer which provides enhanced physical characteristics in the completedunit, is also effective during the fabrication of the unit forsupporting the lead wires with the desired spacing for the capacitorsection for providing mechanical protection for the connections betweenthe lead wires and the capacitor section even before the unit has beenencapsulated.

Accordingly, a further aspect of the invention resides in the method ofmanufacture of capacitors and the like, for facilitating suchmanufactures and for providing improved mechanical properties of theunit during the fabricating procedure.

The nature of the invention and its various further aspects and featuresof novelty will be appreciated from the illustrative disclosure that isgiven in detail below, and from the accompanying drawings which formpart of this disclosure. In the drawings:

FIG. 1 is an enlarged cross sectional view of a capacitor embodyingfeatures of the invention;

FIG. 2 is an enlarged plan view of a Wafer which is shown in sectionFIG. 1;

FIG. 3 is an enlarged end view of the components in FIG. 1 prior toencapsulation; and

FIG. 4 is an approximately accurate full-size view of a typicalcapacitor such as that illustrated in FIG. 1.

Referring now to the drawings, a capacitor section 10 is shown havingterminals that are connected to lead wires 12 by means of conductiveepoxy cement 14. As illustrated in FIG. 3, lead wires 12 have flattenedend portions 12a that are covered by the conductive cement 14. Capacitorsection 10 is of a conventional construction commonly termedextended-foil section, wherein two strips of metal foil areconcentrically wound, the successive convolutions being separated fromeach other by wound strips of dielectric material. One strip of foil isshifted axially relative to the other foil and the dielectric strips sothat its edge projects at one end of the wound section whereas the otherfoil has its edge disposed outward of the edges of the dielectric stripat the opposite end of the wound section. The projected foil 10a has itsopposite edge 10!) recessed relative to the edge of the dielectricmaterial. By like token, the projected foil 10d has an inwardly offsetedge 10:: that is recessed relative to the opposite edge 10] of theinsulating dielectric strip and relative to the projected-foil edge 10a.Such wound extended-foil capacitor sections are well-known. They can becade extremely small and have relatively large values of capacitancewhere the dielectric strips used are of extremely thin material such as0.00015 Mylar. Where such units are extremely small the customarydifficulty of making connection to the foils, which are almost always ofaluminum, is made even more even more difiicult. Also, where thecapacitor section is extremely small, the possibility of damageresulting from soldering or even from spotwelding may be a problem, butthe problem is avoided by use of conductive cement, particularlyconductive epoxy cement.

A wafer 16 of insulating material such as nylon is disposed adjacent thecapacitor section 10. The lead wires 12 extend through holes 16a in thewafer with the flat end portions 12a of the wires adjacent the wafer.The wires 12 are tightly held and accurately positioned by the wafer 16.This is extremely useful during the further assembly operation in themanufacture of capacitors since the lead wires 12 are precisely locatedand snugly accommodate the capacitor section 10 therebetween. The wafer16 is tough i.e., strong but flexible and not brittle. The thickness ofthe wafer relative to its width and length is selected so that it isrelatively inextensible. Once the capacitor body has been positionedbetween the opposed lead ends 12a the previously described conductiveepoxy cement 14 is applied to physically and electrially bond the leadwires to the opposed ends of the capacitor section 10. I

The capacitor section 10, lead wires 12, and wafer 16 are then unitedinto a mechanically strong and hermetically sealed capacitor unit 18 bya hard moisture-excluding insulation 20 that is applied as a coating.Encapsulating coatings, selected from thermosctting epoxy resins havingthe desired insulating and moisture excluding characteristics, areusually quite brittle, separately. However, where the insulator Wafer 16is contained and encapsulated in the same coating 20 that encapsulatesthe capacitor section 10, the wafer and the insulating coating are eacheffective to modify the characteristics of the other. The capacitorsection 10, wafer 16, and adjacent portions 12a of the lead wires 12 areimmersed in a liquid epoxy coating which is then set as by baking. Thewafer is surrounded and supported by the epoxy coating 18 whicheffectively rigidizes the wafer. The depth of immersion or dipping iscarefully controlled to minimize the extent of the coating 18 on thelead wires 12 beyond the Wafer 16. As a result of the hard coating 18being present about the wafer, mechanical stresses imposed on the leadwires 12 have no tendency to twist or bend the wafer 16. Further,because of the restraint imposed by the relatively inextensible water,the leads have no tendency to crack the hard encapsulating coating 18.The efiects of the mechanical stresses on the joints between the leadwires 12 and wound section 10, such as encountered during installationor during use of the capacitor, are minimized by the wafer 16 which isrigidized by the hard coating 18.

The above described method and construction may be utilized to greatadvantage in the production of other types of encapsulated components.The toughness of the wafer allows the selection and use of encapsulatingcoatings which might otherwise not be selected even though they havecertain other desirable characteristics such as high insulation value,good thermal conductivity, or good moisture-excluding properties.

Although one embodiment of the invention has been shown and described,it will be apparent to those skilled in the art that variousapplications and modifications may be made of the novel features withoutdeparting from the spirit and scope of the invention.

What I claim is:

1. The method of manufacturing an encapsulated component including thesteps of frictionally inserting two individual lead wires into spacedapart lead wire receiving apertures in a water of tough, relativelyinextensible insulation material so that said lead wires have alignedends projecting beyond said wafer for receiving and resiliently engagingsaid component therebetween, said apertures being spaced apart thelength of the component to be encapsulated, inserting said component tobe resiliently engaged and held between and by said aligned ends of saidlead wires with the terminal portions of said component in registrationwith said projecting ends of said lead wires, mechanically andelectrically joining said projecting ends and said terminal portions ofsaid component, and encapsulating said wafer, said component, and saidprojecting ends of said lead wires in a moisture-excluding, hard,relatively brittle insulation coating to rigidize said water and formthe exterior of said encapsulated component.

2. The method of manufacturing an encapsulated capacitor which has awound capacitor section of the extended foil type, said capacitorsection being provided with terminal portions at the opposite endsthereof, including the steps of frictionally inserting two individuallead wires each having a flattened end portion into spaced apart leadwire receiving apertures in a water of tough relatively inextensibleinsulation material, so that said lead wires have said flattened endportions aligned with one another and projecting beyond said water forreceiving and resiliently engaging said capacitor section therebetween,said apertures being spaced apart the length of said capacitor section,inserting said capacitor section to be resiliently engaged and heldbetween and by said ends of said lead wires with said flattened ends ofsaid lead wires in engagement with said terminal portions of saidcapacitor section, mechanically and electrically joining said flattenedWire ends and said capacitor section, and encapsulating said wafer, saidcapacitor section, and said flat ends of said lead wires in amoisture-excluding hard, relatively brittle, insulation coating torigidize said wafer, and form the exterior of said capacitor.

References Cited by the Examiner UNITED STATES PATENTS 2,41 ,539 12/1946Ballard 339--275 X 2,745,045 5/1956 Ingram 264272 X 2,766,510 10/ 1956Heibel.

2,809,332 10/ 1957 Sherwood 264-272 X 2,857,560 10/1958 Schnable et al.264272 X 2,954,117 9/ 1960 Freeburg.

3,110,787 11/1963 Borzoni 200'-120 X 3,111,612 11/1963 Lehmann 317101 X3,227,841 1/1966 Gaia 200 X JOHN F. CAMPBELL, Primary Examiner.

R. W. CHURCH, Assistant Examiner.

1. THE METHOD OF MANUFACTURING AN ENCAPSULATED COMPONENT INCLUDING THESTEPS OF FRICTIONALLY INSERTING TWO INDIVIDUAL LEAD WIRES INTO SPACEDAPART LEAD WIRE RECEIVING APERTURES IN A WAFER OF TOUGH, RELATIVELYINEXTENSIBLE INSULATION MATERIAL SO THAT SAID LEAD WIRES HAVE ALIGNEDENDS PROJECTING BEYOND SAID WAFER FOR RECEIVING AND RESILIENTLY ENGAGINGSID COMPONENT THEREBETWEEN, SAID APERTURES BEING SPACED APART THE LENGTHOF THE COMPONENT TO BE ENCAPSULATED, INSERTING SAID COMPOENT TO BERESILIENTLY ENGAGED AND HELD BETWEEN AND BY SAID ALIGNED ENDS OF SAIDLEAD WIRES WITH THE TERMINAL PORTIONS OF SAID COMPONENT IN REGISTRATIONWITH SAID PROJECTING ENDS OF SAID LEAD WIRES, MECHANICALLY ANDELECTRICALLY JOINING SAID PROJECTING ENDS AND SAID TERMINAL PORTIONS OFSAID COMPONENT, AND ENCAPSULATING SAID WAFER, SAID COMPONENT, AND SAIDPROJECTING ENDS OF SAID LEAD WIRES IN A